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Supporters of the woman who murdered her severely autistic daughter are organising a nationwide protest against her incarceration and the agencies that, they claim, failed her.

Donella Knox drugged and smothered her 20-year-old daughter last year after she felt helpless about Ruby's deteriorating health and suffering. Knox felt forgotten about and ignored by the health and care systems.

Donella Knox, 49, appears in court. She admitted to murdering her 20-year old daughter Ruby on May 17 at their Blenheim home. PHOTO/POOL

Donella Knox, 49, appears in court. She admitted to murdering her 20-year old daughter Ruby on May 17 at their Blenheim home. PHOTO/POOL

Ruby Isabella Knox, born in Blenheim on January 8, 1996, was severely intellectually disabled and diagnosed with severe autism spectrum disorder. She also suffered from a litany of health problems, including chronic constipation and haemorrhoids, incontinence, spina bifida, gastroesophageal reflux disease, asthma, rhinitis, menstrual difficulties, and hip pain. She couldn't talk, nor did she have any ability to empathise.

Ruby was prone to killing pets or small animals. The pair couldn't enjoy play dates or socialise with other families. Instead, they were all alone in their Blenheim state house.

Ruby Knox was smothered to death when she was 20 years old last year in her Blenheim home. PHOTO/supplied

Ruby Knox was smothered to death when she was 20 years old last year in her Blenheim home. PHOTO/supplied

Butcher witnessed Ruby in some of her worst states. Her and Knox would meet up with their children when they both lived in Nelson. She said Ruby got really excited when she was taken out of the house. She'd be smiling and happy. But then once she approached you she would attack.

"You'd go 'hello Ruby' and she'd just claw your face out and try to strangle you even though she was happy to be out of the house.

"We couldn't take her to the park or the beach because she'd attack the other children and animals. Every time."

Knox travelled across New Zealand, and even to the United States, seeking expert help. Isolated, exhausted and depressed, she often wondered if things would ever get better.

On May 16 last year, she finally snapped. She murdered Ruby.

A letter had arrived in the post that morning from doctors saying they could find "no obvious reason" for Ruby's seemingly worsening pain.

Justice Joe Williams who last December at the High Court in Blenheim jailed Donella to four years in jail for Ruby's murder, said it appeared that the letter was "a trigger for your decision to take Ruby's life".

At around 1pm that day, she sedated Ruby with 20.5mgs of risperidone anti-psychotic medication before placing both hands over her face and nose until her breathing stopped.

Donella then went to Blenheim police station and gave a full confession.

Butcher said that even though Knox was allocated respite care she couldn't take it as there were no qualified carers in her region.

Butcher also claimed that Knox was made to feel "wrong and inadequate" when she repeatedly went to the hospital to get Ruby tested as she was in pain. The tests came back negative but Butcher said it was later found the rods in Ruby's back were pinching her.

She said there were instances where Knox would turn up to a doctor's appointment and they hadn't been sent the right notes for Ruby and didn't understand the case.

"A lot of time the agencies miscommunicate with each other so the people get failed non stop."